There is no such thing as "battle" magic if you are talking about things such as you read in books or see in Hollywood films. Nope, nor wizard's duels either. Real magic is far more subtle than that and works in its own time and pace.

It takes time for real magick to work. You also get what you put into it. If you do a half-bit job, you'll get a half-bit result. If you put all your effort into it and do a full-bit job, you'll get a full-bit result.

As stated above me, magick doesn't happen instantaneously. It is subtle. The only kind of offensive magick would be like curses our hexes. There are however spells for protection, and you can make a shield around you with energy. You could possibly reconfigure, reprogram, or reshape your aura to be spiked or repelling to others.
If you want to practice battle magick as you call it, you should also be very adept at defensive/protective and healing magick.